Electrical submersible pumps (ESP) are widely used to pump oil production wells. A typical ESP has a rotary pump driven by an electrical motor. A seal section is located between the pump and the motor to reduce the differential between the well fluid pressure on the exterior of the motor and the lubricant pressure within the motor. A drive shaft, normally in several sections, extends from the motor through the seal section and into the pump for rotating the pump. The pump may be a centrifugal pump having a large number of stages, each stage having an impeller and diffuser.
During operation, the impellers create thrust, which can be both in downward and upward directions. The impellers transmit the thrust in various manners to the diffusers. Some pumps are particularly used in abrasive fluid environments. In those pumps, an abrasion resistant thrust runner may be coupled to the shaft to receive thrust from one or more impellers. A bushing may be secured into a receptacle in the diffuser to transfer the thrust. The thrust runner and the bushing may be formed of an abrasion resistant material such as tungsten carbide, that is harder than the material of the diffuser. The bushing is commonly installed in the receptacle with a press fit.
Damage and misalignment may occur when the hard metal bushing is press fit into the diffuser. The wear resistant bushing may misalign slightly when pressed into the bearing carrier. Load concentrations may occur, causing the brittle carbide material to crack. Some pumps tend to vibrate, particularly at higher fluid flow pressures, and the vibration can lead to carbide chattering and cracking.
An electrical submersible pump assembly has a plurality of modules, including a rotary pump module, a motor module, and a seal section module located between the motor module and the pump module. A bearing in at least one of the modules has a sleeve coupled to a drive shaft in said one of the modules for rotation therewith. A bushing has a bore that receives the sleeve in sliding, rotational engagement. A stationarily mounted supporting member has a receptacle that receives the bushing. The supporting member is of a material having less hardness than the material of the bushing. The bushing has an exterior portion of smaller diameter than a portion of the receptacles defining an annular gap. An elastomeric radial compliant member in the gap allows limited radial movement of the bushing relative to the supporting member. For axial compliance, the bushing is free to move axially a limited amount relative to the receptacle.
A key and keyway arrangement may be between the bushing and the supporting member for preventing rotation of the bushing relative to the supporting member. The key and keyway arrangement may include a key integrally formed on the bushing and a slot in the receptacle.
The radial compliant member may comprise at least two elastomeric rings. Alternately, the compliant member may comprise a layer of elastomeric material bonded to the bushing and to the receptacle.
A resilient axial compliant member may be positioned to urge the bushing upward relative to the receptacle. In one embodiment, the axial compliant member comprises an elastomeric ring. In another embodiment, the layer of elastomeric material extends between a thrust receiving shoulder of the receptacle and the bushing to serve as an axial compliant member.
The pump may be a centrifugal pump having a plurality of stages, each of the stages having an impeller and a diffuser, with the bearing being located in at least one of the stages. The sleeve in that instance composes a thrust runner that receives thrust from the impeller of one of the stages and has a thrust transferring face in engagement with a thrust receiving end of the bushing. The bushing has a thrust transferring surface that engages a thrust receiving shoulder in the receptacle of said one of the stages. The supporting member comprises a diffuse, or it could be a bearing spacer.